This invention relates to a keyboard musical instrument and, more particularly, to a keyboard musical instrument equipped with an information processing system and a data acquisition system for generating music data information representative of a performance on the keyboard musical instrument.
An automatic player piano is categorized in the keyboard musical instrument. The automatic player piano is based on an acoustic piano, and an automatic playing system and a data acquisition system are assembled with the acoustic piano. While a pianist is playing a tune on the acoustic piano, the data acquisition system monitors the keys to see whether or not the pianist depresses any one of the keys. When the data acquisition system notices a key moving from the rest position toward the end position, the data acquisition system specifies the key and the key velocity, and generates a piece of music data information representative of the key motion. The data acquisition system successively generates pieces of music data information during the performance. The pieces of music data information are stored in a suitable memory for playback. Otherwise, the data acquisition system formats the pieces of music data information into music data codes, and supplies the music data codes to another musical instrument such as, for example, an electric keyboard for producing the electronic sounds.
The prior art data acquisition system has an array of key sensors, which are assigned to the keys of the keyboard, respectively. The key sensor is broken down into a pair of photo couplers and a shutter plate. The shutter plate is attached to the lower surface of the associated key, and downwardly projects therefrom. The photo couplers are provided under the associated key, and are arranged along the trajectory of the shutter plate. When the key is depressed, the shutter plate is downwardly moved together with the key, and sequentially interrupts the light beams of the photo couplers. The detecting signals are sequentially supplied from the photo couplers to a data processing unit. The data processing unit specifies the depressed keys and determines the key velocity on the basis of the time period between the interruption at the first photo coupler and the interruption at the next photo coupler. The key velocity determines the loudness of the sound to be proportional thereto. The data processing unit further estimates a time to strike the associated music string with the hammer on the basis of the key velocity and the time to be interrupted by the shutter plate.
If the player simply depresses all the keys from the rest positions to the end positions, the prior art data acquisition system will generate a set of music data codes exactly representing the original performance. However, such fingering is rare. A pianist repeats the depression without reaching the rest position. The times to strike the music string are different from those stored in the music data codes, and the loudness of the actual sound is deviated from the loudness stored in the music data code. For example, a player is assumed to insert a repetition in his performance. The keystroke is short, and the actual piano sound is weak. However, the key velocity is large, and the large loudness is stored in the music data code. If the automatic player reproduces the sound on the basis of the music data code, the hammer violently strikes the music string, and makes the reproduced sound different from the original sound.
A countermeasure has been proposed. In order to exactly determine the loudness of the actual sound, hammer sensors are attached to the acoustic piano. FIG. 1 shows the prior art hammer sensors 70 associated with one of the hammers. In the following description, term xe2x80x9cfrontxe2x80x9d is indicative of a position closer to a player sitting for playing a tune on the keyboard, and, accordingly, term xe2x80x9crearxe2x80x9d is indicative of a position farther from the player than the front position. Term xe2x80x9clateralxe2x80x9d is indicative of a direction in which the keys are arranged on a key bed.
The hammer is broken down into a hammer shank 43 and a hammer head 44. The hammer shank 43 upwardly projects from a hammer butt 41, and the hammer head 44 is fixed to the leading end of the hammer shank 43. Reference numeral 46 designates a catcher frontward projecting from the hammer butt 41.
A shutter plate 71 and a photo coupler 77 serve in combination as the hammer sensor 70. The shutter plate 71 is attached to the hammer shank 43, and rearward projects form the hammer shank 43. The shutter plate 71 is moved together with the hammer shank 43, and is movable with respect to the associated music string S. A slit 71a is formed in the leading end portion of the shutter plate 71. On the other hand, the photo coupler is attached to brackets, and is stationary with respect to the associated music string S. The photo coupler 77 consists of a light emitting element and a light detecting element, and a light beam P is radiated from the light emitting element to the light detecting element. When the hammer is staying at the rest position, the shutter plate 71 is spaced from the light bean P as indicated by the real line, and the photo coupler supplies a hammer position signal of a high voltage level to a data processing unit (not shown).
A player is assumed to depress the associated key. The depressed key actuates the associated action mechanism, and the action mechanism drives the hammer for rotation. When the hammer reaches an intermediate position H2, the shutter plate 71 interrupts the light beam P at the leading end thereof, and the hammer position signal falls to a low voltage level. The data processing unit acknowledges that the hammer head 44 reaches the intermediate position H2. The hammer is further rotated, and reaches the next intermediate position H3. Then, the slit 71a is aligned with the light beam P, and the photo coupler 71 recovers the hammer position signal to the high voltage level. The data processing unit acknowledges that the hammer reaches the next intermediate position H3. The distance between the intermediate positions H2 and H3 is known, and the data processing unit is notified the times when the hammer shank 43 reaches the intermediate position H2 and the intermediate position H3. The data processing unit determines the interval between two interrupting times, and calculates the hammer velocity between the intermediate positions H2 and H3. The intermediate positions H2 and H3 are arranged in such a manner as to be close to the final position where the hammer head 44 strikes the music string S, because the hammer velocity is exactly proportional to the intensity of the impact between the hammer head 44 and the music string S and, accordingly, the loudness of the original sound. The prior art data acquisition system formats the piece of music data information exactly representative of the loudness. When the automatic playing system reproduces the sound on the basis of the music data codes, the hammer strikes the music string S at the intensity equal to that in the original performance, and the music string S reproduces the sound at the original loudness.
The hammer sensors 70 are expected to detect the hammer velocity in the monitoring section between the intermediate positions H2 and H3 arranged to be as close to the music string S as possible. However, it is impossible to keep all the hammer sensors at the appropriate positions. This is because of fact that the distance between the hammers at the rest positions and the associated music strings S is varied. The variance is of the order of 2 millimeters in standard grand pianos.
In detail, the hammers are rotatably supported by a shank flange rail, which in turn is supported by the action brackets. The action brackets are mounted on the key bed. The total weight of the hammers is exerted on the shank flange rail, and the shank flange rail is less deformed. The action mechanisms are also supported by the action brackets. However, the total weight of the hammers, the action mechanisms, the action brackets and the keyboard is not so large that the key bed can support them without substantial deformation. For this reason, the rest positions of hammers are stationary over the key bed. On the other hand, the strings are stretched over a frame, and are anchored at ends thereof to the pitch pins and at the other ends thereof to the tuning pins. The total tension is of the order of 20000 kg. Although the frame is formed of cast iron, the frame is deformed due to the large tension, and the distance between the key bed and the music strings S is not constant.
As shown in FIG. 2, the key bed KB horizontally extends between both end portions of the side board SB, and the music strings S are stretched over the key bed KB. The distance between the key bed KB and the music strings S is increased from the higher-pitched part toward the lower-pitched part. The distance at the rightmost music string S is 196 millimeters, and is increased to 197 millimeters at the center music string S. The difference is 2 millimeters. Even if the rightmost hammer sensor 70 is adjusted in such a manner that the intermediate positions H2 and H3 are spaced from the associated music string S by 5.5 millimeters and 0.5 millimeter, the hammer sensor 70 for the center music string has the intermediate positions H2 and H3 at 7.5 millimeters and 2.5 millimeters spaced from the center music string S. The data processing unit determines the hammer velocity in the different parts of the trajectories of the hammers, and the reproduced sounds are not always equal in loudness to the original sounds. Moreover, the hammer sensors 70 are supported by the brackets as described hereinbefore. If the brackets are deformed, the difference becomes further serious.
The difference in monitoring section has serious influences on the loudness of reproduced sounds. When a pianist ordinarily depresses a key, the hammer strikes the associated music string through uniform motion. The hammer velocity is considered to be constant, and the difference between the initial hammer velocity and the final hammer velocity is ignoreable. The hammer velocity at an arbitrary part of the trajectory is considered to be proportional to the loudness. If the pianist softly depresses the key, the hammer is also driven for rotation at the escape of the jack from the hammer butt. However, the hammer is decelerated after the escape.
Only the hammer velocity immediately before the strike is proportional to the loudness. Thus, it is important to determine the hammer velocity in the final part of trajectory immediately before striking the music string.
In general, the longer the monitoring section, the higher the precision. It is desirable to prolong the monitoring section between the intermediate positions H2 and H3 in so far as the hammers are considered to travel through the uniform motion. However, a short monitoring section is desirable for the hammers gradually decelerated toward the music string. Thus, the appropriate monitoring section is to be varied depending upon the hammer motion.
As described hereinbefore, the prior art hammer sensors 70 have the monitoring sections, which are constant in length and unintentionally moved on the trajectories of the hammers due to the deformation of the frame. When the manufacturer regulates the monitoring sections individually, a large amount of time and labor is consumed, and a special regulating mechanism is required for the hammer sensors 70. This results in increase of the production cost. After the delivery, it is quite difficult to tune the hammer sensors. This is the first problem inherent in the prior art data acquisition system incorporated in the keyboard musical instrument such as the automatic player piano.
On the other hand, if the manufacturer delivers the products of the prior art automatic player piano without any regulation, a set of music data codes does not exactly represent the original performance, and another problem is encountered in the fidelity. The prior art automatic player piano is usually responsive to a set of music data codes recorded through another keyboard musical instrument. The music data codes have been normalized, and the pieces of music data information stored therein are individuated for the prior art automatic player piano used in the playback. The individuality of the prior art automatic player piano is determined on the basis of pieces of data information obtained through the hammer sensors 70. If the monitoring sections are unintentionally moved on the trajectories of the hammers, the difference among the monitoring sections has influences on the individuality, and the reproduced sounds are different from the original performance. Thus, the second problem is the fidelity in the playback.
It is therefore an important object of the present invention to provide a keyboard musical instrument, which faithfully reproduces an original performance without complicated tuning.
It is also an important object of the present invention to provide a data acquisition system, which exactly determines a physical quantity of moving objects incorporated in a keyboard musical instrument.
To accomplish the object, the present invention proposes to monitor a moving object in a whole range of motion.
In accordance with one aspect of the present invention, there is provided a keyboard musical instrument comprising a keyboard having at least one key manipulated by a player, at least one beating member linked with the at least one key and moved between a rest position and an impact position when the at least one key is manipulated, a beaten member struck with the at least one beating member at the impact position, at least one sensor continuously monitoring the at least one beating member moved between the rest position and the impact position for producing an output signal representative of a physical quantity of the beating member in the range between the rest position and the impact position and an information generating system connected to the at least one sensor and generating pieces of data representative of a motion of the at least one beating member on the basis of the output signal.
In accordance with another aspect of the present invention, there is provided a data acquisition system for a moving object comprising at least one sensor monitoring the moving object in a whole range of motion thereof for producing a first output signal representative of a continuous variation of a physical quantity of the moving object and a data processing system connected to the at least one sensor and extracting pieces of data information from the variation of the physical quantity for producing a second output signal representative of a meaning of the motion.